1. Technical Field of the Invention
The embodiments of the invention relate to the charging of rechargeable batteries and, more particularly, to utilizing a DC-DC converter circuit of an integrated circuit chip to charge a battery.
2. Description of Related Art
A variety of electronic equipment, especially portable or handheld electronic devices, are capable of being powered from a battery. Some of these portable and/or handheld devices include, but are not limited to, laptop or notebook computers, personal digital assistants (PDAs), compact disc (CD) players, digital video disc (DVD) players, MP3 (an audio standard under the Moving Picture Experts Group or MPEG) players, AM/FM (amplitude modulation/frequency modulation) radios, pagers, cellular telephones, etc. These devices typically contain one or more integrated circuit chip(s) to perform the operations(s) intended by the device. Many, if not most, of these devices may be powered by self-contained power sources, such as a battery. In many instances, the batteries may be rechargeable.
When a rechargeable battery is present in a portable or handheld device, the battery may be recharged by the use of an internal or an external battery charger. In some instances, it may be desirable to have an internal battery charger so that a separate external charger unit is not needed.
In a typical setup to charge a rechargeable battery, where the battery charging is provided by an internal battery charger, the device or chip includes a battery charging circuit to charge the battery. Typically, a separate and distinct battery charging circuit is utilized and this charging circuit is activated when an external power source is coupled to the device. For example, the charging of the battery by the charging circuit commences when the device is coupled to an external power source, such as a wall outlet. However, in some instances, external power is provided by other sources, rather than the alternating current (AC) power source.
As an example, in today's applications, certain interfaces may provide power through the interface itself. A bus specification, such as a Universal Serial Bus Revision 2.0 specification (USB 2.0), provides not only protocol for data transfer between two devices, but the USB 2.0 bus specification also provides a power link between a USB host and a USB device coupled onto the USB. For example, a peripheral device (such as an MP3 player), when coupled to a host (such as a personal or laptop computer) through a USB 2.0, the USB link not only provides the data lines for data transfer between the two devices, but +5 volts (nominal) is also provided to the peripheral through the interconnect. Thus, devices coupled onto the USB 2.0 may utilize the voltage provided on the bus to power circuitry of the peripheral component.
Accordingly, it would be advantageous to utilize the power supplied by an interconnection bus, such as USB 2.0, not only to provide the power to the component for its operation, but to utilize that power also to charge the battery. However, there may be a limitation on the current that may be drawn from such a power source. A general USB hub, for example, may be limited to a current of 0.1 amperes that may be draw from the hub. Thus, current drawn may be a consideration when using such sources for battery charge.
Also, it may be advantageous to combine the DC-DC converter circuit and the battery charging circuit, in order that some circuit components may be used in duplicity to reduce the number of components that may be needed to provide both the DC-DC conversion and battery charging operations.